Circuit Description
The throttle position (TP) sensor 1 and the TP sensor 2 are potentiometer type sensors. Both sensor types have the following circuits:
| • | A 5-volt reference circuit |
| • | A low reference circuit |
| • | A signal circuit |
The TP sensor provides the engine control module (ECM) with a signal voltage proportional to the throttle plate movement. The TP sensor 1 signal voltage at closed throttle is near the 5-volt reference and decreases as the throttle plate is opened. The TP sensor 2 signal voltage at closed throttle is near the low reference and increases as the throttle plate is opened. When the control module detects that the TP sensor 1 and the TP sensor 2 signal circuits are out of correlation with each other, DTC P1221 will set.
Conditions for Running the DTC
| • | The engine is running |
| • | The ignition voltage is more than 5.25 volts. |
| • | DTCs P1635 and P1639 are not set. |
Conditions for Setting the DTC
The ECM detects that the difference between TP sensor 1 and TP sensor 2 is more than the predicted value.
Action Taken When the DTC Sets
| • | The control module stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records. |
| • | The driver information center, if equipped, may display a message. |
Conditions for Clearing the DTC
| • | A current DTC Last Test Failed clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic. |
| • | Clear the DTC with a scan tool. |
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Engine Control Module Connector End Views | ||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||
2 | Observe the DTC Information with a scan tool. Is DTC P1120 or P1220 also set? | -- | Go to Step 3 | |||||||
3 |
Is the resistance more than the specified value for any circuit? | 5ohms | Go to Step 7 | Go to Step 4 | ||||||
4 | Test the signal circuit of the TP sensor 1 for a short to the signal circuit of the TP sensor 2. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 5 | ||||||
5 | Test for an intermittent and for a poor connection at the throttle body harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 6 | ||||||
6 | Test for an intermittent and for a poor connection at the ECM harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 8 | ||||||
7 | Repair the high resistance in the circuit that measured above the specified value. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 9 | -- | ||||||
8 | Replace the throttle body. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 9 | -- | ||||||
9 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 10 | ||||||
10 |
Important: Be aware that repairing one individual condition may correct more than one DTC. Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||
